This invention relates to a fuel injection type four cycle engine and more particularly to an intake system and fuel injection system for such an engine.
The advantages of multiple valve internal combustion engine are well known and such engines are becoming quite popular. The most typical type of multi-valve engine employed today incorporates four valves per cylinder, two intake and two exhaust. However, it has also been acknowledged that the performance of the engine can be further improved through the use of five valve cylinder heads embodying three intake valves and two exhaust valves. However, when the number of intake valves is multiplied above two, there can be certain complexities with the combustion chamber and the porting arrangement for it.
Frequently port type fuel injection is employed with such engines and it is desireable to incorporate a system that does not require a fuel injector for each valve seat of a three valve engine. Although it is relatively simple to employ a single injector for two intake valves, when this principal is implied to three intake valves certain problems arise.
This is particularly true since three valve engines permit the different configurations of the intake porting so as to achieve some form of swirl in the combustion chamber but not so much swirl that the high speed volumetric efficiency of the engine is deteriorated. However, where there are such unequal flows through the intake passages, particularly at low speeds, certain problems arise if attempts are made to employ a single fuel injector. That is, the fuel/air distribution in the cylinder may not be as uniform as desired.
It is, therefore, a principal object to this invention to provide an improved injection and porting arrangement for a multiple valve engine having a siamese type porting system and wherein a single fuel injector supplies fuel substantially equally to all intake ports.
It is a further object to this invention to provide an induction system for a multiple valve engine having at least three valves per cylinder and wherein the flow through the intake valves is not equal under all running conditions so as to achieve some swirling motion in the intake passage and still have equal fuel distribution through the use of a single fuel injector.
One way in which the unequal flow patterns can be achieved is by having a siamese type intake passage serving three intake valves with one of the passages being longer than the other so as to import a higher velocity and swirl to the intake charge. However, where this is done, if the fuel injector is disposed so as to spray fuel into the intake passage at a common portion, the longer passage may receive less fuel than the other passages.
It is, therefore, a still further object to this invention to provide an improved arrangement for insuring equal fuel distribution through a multiple valve internal combustion engine incorporating a single fuel injector per cylinder.